1. Field of the Invention
The present invention relates to a device for testing the rollover threshold of automobiles. More particularly, the present invention relates to a rollover sled test device which allows for the non destructive testing of an automobile""s rollover threshold.
2. Technical Background
Rollover crashes are one of the most significant safety problems for all classes of light vehicles. The problem is especially acute for light trucks such as pickups, sport utility vehicles, and vans. According to one report, light trucks have more than 125 percent more rollover crashes per registered vehicle than passenger cars.
In recent years there have been an average of over a quarter million crashes per year where a rollover was the first harmful event. These rollover crashes result in an average of over 9,000 deaths per year and account for nearly thirty percent of all light vehicle fatalities. Over 200,000 people are injured in rollover crashes each year. Rollovers are second in severity only to frontal crashes.
Most rollovers result from the vehicle leaving the roadway and tripping. Two types of tripped rollovers exist, the soil trip rollover and the curb trip rollover. In the soil trip rollover, a vehicle first begins a lateral slide. As the car leaves the roadway, the tires drag in the soil, and the soil builds up near the tires creating a lip or mound of soil that trips the vehicle and causes a rollover. In the curb trip rollover, the vehicle begins a lateral slide until the wheels contact a curb or other solid, stationary object. The vehicle is tripped by the curb and thrown into a roll.
Vehicle safety is an important part designing and manufacturing a vehicle. Today most cars and trucks have a variety of safety features designed to avoid a crash and to protect the occupants in the unfortunate event of a crash. Devices such as anti-lock brakes help a driver avoid accidents by shortening the distance required to stop a vehicle. Seat belts reduce injury to vehicle occupants in the event of a crash and have been provided in vehicles for decades.
More recently, air bags and inflatable curtains have been installed to protect vehicle occupants in the event of a crash or rollover. The air bags and curtains use computerized and mechanical sensors installed in the vehicle to sense a crash and deploy the device. When the sensor detects a certain type of crash such as a frontal crash or rollover, the air bag or inflatable curtain is deployed protecting the vehicle occupants. If the air bag or inflatable curtain is errantly deployed the vehicle occupants may be injured by the forceful inflation of the safety device. Therefore, it is essential that the sensors be able to detect when a crash actually occurs that requires deployment of the safety device.
However, it is impossible to determine how a car or truck will perform in a crash without actual test data. Vehicle manufactures, consumer groups, and the government test vehicles in a variety of ways to determine vehicle safety and to improve the vehicle safety. In recent years vehicles have been tested in a variety of crash situations. For example, a vehicle may be accelerated down a track and crashed into a solid object such as a wall. The impact of the vehicle into the wall simulates a crash and damages the vehicle. The vehicle may be analyzed for its ability to protect of the driver and passengers from injury in this frontal crash scenario. The data obtained from the crash test simulation may also be used to design sensors to deploy safety devices such as air bags in the event of a frontal crash.
A few methods have been developed for testing the rollover threshold of a vehicle. For example, a car or light truck is subjected to a large lateral acceleration causing the vehicle to skid sideways on its tires. The vehicle then hits a tripping device such as a curb which throws the vehicle into a roll. In this manner a vehicle may be analyzed for its potential to roll and sensors designed to sense a rollover crash. However, this method of testing rollover threshold destroys the vehicle tested and is costly. Because the vehicle is destroyed, only one test can be run per vehicle which limits the amount of data that can be collected and analyzed. Moreover, it is difficult to obtain reproducible data because of the many variables involved in such a test.
A few non-destructive ways for testing the rollover threshold of a vehicle have been developed. Generally these methods comprise attaching stabilizing bars to the sides of the vehicle. The vehicle with the stabilizing bars is driven around a test course. The driver of the vehicle will attempt sharp turns at different speeds which may cause the vehicle to tip. If the vehicle begins to tip into the start of a rollover, the bars contact the ground preventing the completion of the roll. The usefulness of this type of rollover testing is limited, because the test is not capable of simulating the sliding and tripping that most often causes a rollover. Moreover, a driver will not perform the test in the same manner, making the results of the test difficult to reproduce.
Accordingly there is a need in the art for a method and apparatus for testing the rollover threshold of a vehicle. It would be a further advancement in the art if the method for testing the rollover threshold of a vehicle produced reproducible results. Moreover, the cost of rollover testing could be significantly reduced if the method for testing the rollover threshold of a vehicle were non-destructive.
The present invention relates to a rollover sled test device which enables the determination of the rollover threshold of a vehicle. The sled has a carriage that travels on a track from a first track location to a second track location. The carriage is configured so that an actual vehicle can be positioned on the carriage. The vehicle is positioned on the carriage so that a first side of the vehicle faces the first track location and a second side of the vehicle faces a second track location.
An accelerator propels the carriage with the mounted vehicle from the first track location to the second track location. As the carriage nears the second track location, a decelerator abruptly slows and stops the carriage. The momentum of the vehicle continues to carry the vehicle in the direction of the second track location. If the rollover threshold of the vehicle is met, the vehicle may roll from the carriage. An observer may then determine the rollover threshold of the vehicle.
Because an actual vehicle with its own suspension is used, the sled test device allows an accurate simulation of how the vehicle will react under real world conditions. If a vehicle rolls from the sled test device, the vehicle will be severely damaged. Therefore, in certain embodiments, the vehicle may be tethered to the carriage. As the vehicle begins a roll, the tether allows the vehicle to tip and begin a roll, but prevents the destructive rolling of the vehicle from the carriage. If it is desired to test a vehicle""s ability to protect occupants in a rollover event, the tether may be disconnected allowing the vehicle to roll.
In a presently preferred embodiment, one or more stops, positioned near the tires of a vehicle mounted on the carriage, are provided to simulate a curb, built-up soil, or other object that may initiate a roll of the vehicles in real world conditions. As the vehicle rapidly slows, the wheels impact the stops. The vehicle may then rotate about the stops a begin a rollover event. If the vehicle is tethered, the tethers will allow the vehicle to tip, but prevent the completion of the rollover.
A variety of devices and methods may be used to decelerate the carriage. For example in one presently preferred embodiment, a set of at least one pad is positioned on a deceleration track. More than one deceleration track may be used in certain embodiments to create an balanced deceleration on the carriage. As the carriage travels on the track, a latch on the carriage contacts the set of at least one pad, slowing carriage with the attached vehicle. The pads may be metallic, organic, or a composite of organic and metallic.
The pads may be configured to exert a pressure on the track. The pressure may vary from about 0 to about 1,000 PSI. The pressure of the pads on the track may be adjustable. In certain embodiments, the pads may be adjusted as a whole with a change in the pressure in one pad changing the pressure in all the pads. In other embodiments, the pad pressure of each pad may be independent of the pressure in other pads. Where two or more pads are used, the pads may be spaced on the deceleration track. In this manner the deceleration pulse generated by a first pad may be completed before the deceleration pulse of the second pad begins.
The deceleration track may be of a suitable length to allow for the deceleration of the carriage. In certain embodiments a deceleration track of about 6 meters in length may be suitable to properly decelerate the carriage and vehicle.
Other decelerators may be used to decelerate the carriage. Any one of the following non-exhaustive list of decelerators or a combination of decelerators may be used to slow and stop the carriage. The carriage may be decelerated by impacting the carriage into a bent metal bar pulled through a set of rollers. The carriage may also be decelerated by impacting the carriage into one or more springs either in tension or compression. One or more hydraulic syringes may be also used to slow the carriage, by impacting the carriage into the one ore more hydraulic syringes. Additionally, shock absorbers, such as one or more pneumatic or hydraulic shock absorbers may decelerate the carriage through impacting the carriage into the shock absorbers. It will be understood by those of skill in the art, any of the decelerators disclosed herein may be used in combination with the other decelerators disclosed herein or other decelerators.
The invention also relates to a method for employing the rollover sled test device. The method comprises positioning a vehicle on a carriage constructed in accordance with the present invention. The carriage may then be propelled from the first track location to the second track location. The carriage is decelerated to simulate a car sliding on a roadway. An additional step of tethering the vehicle may prevent the destruction of the vehicle and allow multiple test to be performed on the same vehicle. When the carriage includes one or more stops, the method may include impacting the vehicle into the stops.
Thus, the present invention presents a rollover sled test device that can determine the rollover threshold of a vehicle. The results produced from the sled test device are reproducible. Because an actual vehicle is used, the sled test device can more readily determine how a given vehicle will perform in real world conditions. Moreover, because the sled test device provides means to decelerate the carriage rapidly or slowly or with varying pulses, a large numbers of real world scenarios may be tested. Also, the cost of obtaining results using an actual vehicle is reduce by the non-destructive nature of the test when the vehicle is tethered to the carriage.
These and other features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.